In one sense, malware includes unwanted software that is installed on a computer. Malware may be hostile, intrusive, or annoying. It may be designed to infiltrate or damage a computer system without the owner's informed consent. Malware can be relatively benign or severely disruptive. Some malware can spread from computer to computer via networks or the use of removable computer-readable media. Some malware attempts to remain hidden from user inspection while other malware becomes obvious immediately.
The number of malware continues to grow at a phenomenal rate. Vendors that produce malware detection and removal products are continually updating the list of malware their products can detect and remove. Guarding against malware is an ongoing challenge.